for example, it will show all the files in W: that are dupes with anything on the PC, but it won't show the other matching dupe of this duplicate if it's not on W:. Is there to way to compare duplicates of one folder, against the rest of the PC and have both dupe couples show in the results? Thank you

I thought about this too, it's possible.
Since only one duplicate function can be used effectively, this additional function could limit where the duplicates are searched for any existing dupe function.
In code, sizedupe: and sizedupe: withpath:<path> would be two completely different code paths for finding duplicates and I would like to reflect that in the search function name.

If not then why not just have the ability to have sizedupe work against currently enabled filters, search?
IOW, just like in the OP: sizedupe: w:.

OP wants to find and list duplicates everywhere, where only one of the duplicate needs to be in w:

sizedupe: w:
would list results only on the w: drive. Unfortunately, hiding size duplicates on other drives.
whereas:
sizedupewithpath:w:
would list all size duplicates where one of the duplicates is on the w: drive.

OP could search for sizedupe: and sort by path, and just go through all the w: results. Unfortunately, results would not be sorted by size.
Using sizedupe: works best when sorting by size.

Since the search
sizedupe: w:
is not too helpful, perhaps Everything could apply this withpath: option automatically.

Maybe something like sizedupefilter: where it would first do sizedupe: then iterate through the list of filtered files, displaying only those files meeting the current filters, search settings.

This would be pretty much how Everything works now.
To do the opposite would be useful, apply a filter and then search for sizedupe: on those results.
This is also on my TODO list, and will be some sort of view option. eg: View -> Show only duplicate names/size and View -> Show only unique names/size

I've added an optional Size Duplicated column for the next major version of Everything.

When sorting by this column, duplicated sizes are listed first (largest to smallest).
You'll be able to search for anything and sort instantly with this column to find name/size duplicates for the current results.

I don't have release for testing yet, sorry.
There's still a bit more to do before an alpha release.